Additives for alkali cleaning systems

ABSTRACT

LOW FOAMING, COPPER CORROSION INHIBITING, ALL TEMPERATURE ADDITIVES FOR ALKALI CLEANING SYSTEMS CONSISTS OF: (A) A MIXTURE OF SEQUESTERING AGENTS, (B) A MIXTURE OF NONIONIC SURFACTANTS, (C) AN ANIONIC SURFACE ACTIVE AGENT AS A HYDROTROPE, AND (D) WATER. THESE ADDITIVES WHEN EMPLOYED IN TYPICAL USE SOLUTIONS EXHIBIT SYNERGISM IN REGARD TO LOW FOAM CHARACTERISTICS AND COPPER CORROSION INHIBITION.

United States l atent O 3,705,856 ADDITIVES FOR ALKALI CLEANING SYSTEMSRonald M. Sedliar, Grosse Ile, Otto T. Aepli, Southgate, and Perle N.Burkard, Wyandotte, Mich, assignors to BASF Wyandotte Corporation,Wyaudotte, Mich. No Drawing. Filed Sept. 1, 1970, Ser. No. 68,760 Int.Cl. Clld 7/06 US. Cl. 252-156 Claims ABSTRACT OF THE DISCLOSURE Lowfoaming, copper corrosion inhibiting, all temperature additives foralkali cleaning systems consists of: (a) a mixture of sequesteringagents, (b) a mixture of nonionic surfactants, (c) an anionic surfaceactive agent as a hydrotrope, and ((1) water. These additives whenemployed in typical use solutions exhibit synergism in regard to lowfoam characteristics and copper corrosion inhibition.

BACKGROUND OF THE INVENTION 1) Field of the invention The presentinvention relates to liquid additives for alkali cleaning systems. Moreparticularly, the present invention relates to low foaming, coppercorrosion inhibiting additives for caustic soda cleaning systems whichare usable over a wide temperature gradient.

(2) Prior art The use of caustic soda-based systems or use solutions forcleaning in breweries, dairies and the like has long been known. Today,the trend in such industries dictate the use of automatedcleaning-in-place (CIP) systems which has in turn rendered liquidcaustic solutions a prominent and important product. In order tosatisfactorily clean, these products must demonstrate detergency, lowfoam propagation, rinsability and inhibition of hardness precipitation,as well as copper corrosion inhibition in copper brew kettles and thelike. Accordingly, the art has taught the incorporation of additives,such as suitable sequestering agents, e.g. sodium gluconate andethylenediaminetetraacetic acid, wetting agents and the like intocaustic soda C-I-P systems to provide efliective in situ cleaning.

However, these types of additives have limited use since they foamexcessively in C-I-P systems and generally they are limited to the areasin which they may be used. For example, in connection with breweriesbecause of variations in cleaning temperatures at the cellar, brew houseand bottle wash stations, types of soil and construction equipment,e.g., copper kettles, each specific cleaning application requires aspecific C-I-P system.

The present invention seeks to obviate this problem by providing anadditive useful in liquid caustic C-I-P systems which is low foaming,non-corrosive to copper and capable of performing at a wide temperaturevariant thereby rendering it extremely useful in breweries and the like.

SUMMARY OF THE INVENTION The present invention resides in a liquidadditive for use in liquid caustic cleaning systems. Broadly speaking,the liquid additive consists of an aqueous solution of: (a) a mixture ofsequestering agents, (b) a mixture of nonionic surface active agents,and (c) a hydrotrope or solubilizing agent which is an anionic surfaceactive agent.

In preparing a typical use solution containing from about 5,000 to50,000 p.p.m. of caustic soda the additive is employed in an amountranging from about 500 p.p.m. to 100,000 p.p.m.

Patented Dec. 12, 1972 For a more comprehensive discussion of thepresent invention reference is made to the following detaileddescription and examples thereof.

DESCRIPTION OF THE PREFERRED- EMBODIMENTS The present invention providesa novel liquid additive for liquid caustic soda cleaning systems,preferably, C-I-P systems, and novel use solutions prepared therefrom.As hereinbefore mentioned, the present additives consist of (a) ahydrotrope which is an anionic surfactant, (b) a mixture of sequesteringagents,

(c) a mixture of nonionic surfactants, and

(d) water.

It has been found that this additive, which is more particularlydescribed hereinafter, when employed in typical use solutions exhibitssynergism in regards to both low foam characteristics and coppercorrosion inhibition.

The hydrotrope or solubilizing agent as hereinbefore noted is anionicsurfactant which is a phosphate ester, and more precisely an alkylphenolpolyglycol ether phosphate.

This product which is more particularly described in US. Pat. No.3,235,627, the disclosure of which is hereby incorporated by reference,is sold commercially by Rohm and Haas under the name Triton 11-66.

It should be noted that in the reference patent the hydrotrope isreferred to as a phosphate ester of a hydroxylic organic compound. Inits presently available commercial form, Triton H-66 is provided as apotassium salt of the phosphate ester as a 50% solids aqueous solutionand is characterized by a viscosity of centipoises at 25 C., a specificgravity of 1.26, a pH of 8-10 in 5% aqueous solution and a freezingpoint of 20 C.

The mixture of sequestering agents contemplated for use herein consistsof a mixture of (1) a,a',rx"-amil10 tris-(methyl phosphonic acid), acomposition corresponding to the formula:

H: P O3H2-CHa-I ICHs-P 01-11, or the potassium or sodium salt thereof,and (2) an alkali metal salt of a sugar acid. By the term sugar acid, asused herein, is meant the fermentation acids as Well as the aldonic anddibasic acids produced from sugars by chemical oxidation. Representativeof this class of acids are, for example, lactic acid, citric acid,gluconic acid, 2-ketogluconic acid, glucoheptonic acid, tartaric acid,arabonic acid, galactinic acid, saccharic acid, mucic acid, and thelike.

Typical alkali metal salts of the sugar acids are, for example, sodiumlactate, sodium citrate, potassium sodium tartrate, sodium arabonate,sodium gluconate, sodium galactonate, sodium Z-ketogluconate, potassiumsodium saccharate, sodium mucate and sodium glucoheptonate as well asmixtures thereof. These compounds and their use as sequestering agentsis more particularly described by Mehltretter et al., Industrial andEngineering Chemistry, v. 95, No. 12, December 1953, at page 2782, thedisclosure of which is hereby incorporated by reference. In the practiceof the present invention it is preferred to employ either sodiumgluconate or sodium glucoheptonate as the salt of the sugar acid.

In preparing the present additive, the mixture of sequestering agents isprepared such that the weight ratio of alkali metal salt of sugar acidto a,a',a"-amino tris- (methyl phosphonic acid) or potassium or sodiumsalt thereof ranges from about 15:1 to 25:1 and preferably from about18:1 to 22:1.

The mixture of nonionic surfactants contemplated for use herein consistsof a mixture of (1) the ethoxylatcd and propoxylated adducts ofethylenediamine, such as described in US. Pat. No. 2,979,528, and (2)either an alkoxylated linear aliphatic alcohol or apolyoxyethylenepolyoxypropylene block copolymer, such as described inUS. Pat. No. 2,674,619, or mixtures thereof.

It has been found that not all of the above-described nonionicsurfactants can be employed herein, but rather only those which exhibitlow foam characteristics can be used. Thus, the nonionic surfactantsgenerally described in US. Pat. 'No. 2,979,528, the disclosure of whichis hereby incorporated by reference, are restricted to those compoundscorresponding to the formula:

having a total molecular weight of from about 900 to 7,800 and whereinis an integer sufficiently large to insure that the ethylene oxidepresent constitutes a maximum of about 10% by weight of the totalmolecular weight of the molecule.

These compounds, as are described in the reference patent, are preparedby the sequential addition of propylene oxide and ethylene oxide toethylenediamine under suitable oxyalkylation conditions.

The alkoxylated linear aliphatic alcohol or ethoxylated linear aliphaticalcohol nonionic surfactants are prepared by the condensation reaction,in the presence of a suitable oxyalkylation catalyst, of ethylene oxideand the alcohol. Generally the alcohols have from about 10 to 20 carbonatoms. These surfactants, which are widely known and commerciallyavailable, generally comprise from about 20 to 80% by weight of ethyleneoxide, based on the total molecular weight of the surfactant. Sometimesethoxylated" aliphatic alcohols contain some propylene oxide as well asethylene oxide when purchased in commercial form. The propylene oxideusually comprises no more than about 30% by weight of the totalmolecular weight of the product, but more may be present depending onthe commercial source of the product. It is the ethylene oxide, though,that enhances the surface active properties of these compounds.Accordingly, as used herein and in the claims appended hereto, the termethoxylated linear aliphatic alcohol includes the products which containthis minor component, propylene oxide.

The polyoxypropylene-polyoxyethylene block copolymers of U8. Pat. No.2,674,619, the disclosure of which is hereby incorporated by reference,which are suitable for use herein are those compounds corresponding tothe formula:

having a molecular weight of from about 900 to 4,500 and wherein a+c aresufficiently large such that the ethylene oxide comprises from about toof the total molecular weight of the compound. These compounds aregenerally prepared by the condensation reaction of ethylene oxide andpolypropylene glycol, polypropylene glycol being, in turn, thecondensation reaction product of propylene oxide and propylene glycol.

In the practice of the present invention the mixtures of nonionicsurfactants are prepared or utilized in a weight ratio of (1) to (2)ranging from about 2:1 to 1:2. Preferably a weight ratio of 1:1 isemployed in preparing and utilizing the mixture.

In preparing the present additives composition, the ingredients thereofare combined in approximately the following weight proportions; based on100 parts thereof:

4 Ingredients: Parts by weight Hydrotrope 1.0 to 9.0 1st sequesteringagent 0.5 to 3.0 2nd sequestering agent 6.5 to 45.0 1st nonionicsurfactant 0.5 to 5.0 2nd nonionic surfactant 0.5 to 5.0 Water 91.0 to33.0

Thus, it is seen that the present additives consist of (a) from about 1to 9 percent by weight of hydrotrope, (b) from about 7 to 48 percent byweight of the mixture of sequestering agents,

(c) from about 1 to 10 percent by weight of the mixture of nonionicsurfactants, and (d) from about 33 to 91 percent by weight of water.

The additive is prepared by simply mixing the ingredients together,maintaining the hereinbefore described proportions and Weight ratios, atambient conditions, i.e., room temperatures and pressures, no specialhandling procedures are necessary.

In preparing a typical use solution employing the present additives, allthat is required is the simple addition of the additive to the usesolution, with mixing. Generally, a caustic soda use solution willconsist of (a) from about 5,000 to 50,000 parts per million (p.p.m.) ofliquid caustic, (b) from about 500 to 100,00 ppm. of additive, and (c)the balance being water.

The present additives can also be directly incorporated into a liquidcaustic wherein they will be present in an amount ranging from about0.05% to 10% by weight, based on the weight of the liquid caustic. Whenadded directly to caustic soda, it is preferred to employ from about0.1% to 5% by weight of additive, based on the weight of the caustic.

In addition to the hereinbefore mentioned properties of the presentadditives, i.e., synergism in regard to low foam propagation and coppercorrosion inhibition, they exhibit another. distinct property in typicalbrewer-adapted use solutions in that the resulting use solutions workefiicaciously over a wide temperatureg radient. The import of this isreadily ackowledged by virtue of the fact that heretofore it wasnecessary to have separate cleaning systems for the cellar, thebrewhouse, and the bottle washing station, due to the differenttemperatures thereat. The present use solution can be used in all threeareas.

For a more complete understanding of the present invention, reference ismade to the following examples, which are not to be construed as undulylimiting the invention. In the examples all parts and percentages are byweight, absent indications to the contrary.

EXAMPLE I An additive was prepared in accordance with the presentinvention by mixing together at about 75 F., the following:

1 Triton 11-66.

a.,a',a.-amino trls-(methyl phosphonic acid).

3 Sodium glucoheptouate.

An ethoxylated adduct of the condensation product or ethylenediamine andpropylene oxide having an average molecular weight of from about 2750 toabout 3350 and containing about 10% by weight of ethylene oxide.

5 A modified ethoxylated and propoxylated adduct of a fatty alcoholhaving a molecular weight of about 770, the ethylene oxide and propyleneoxide being present in a weight ratio of about 4: 1 and soldcommercially by Rohm and Haas under the name Triton DF-12.

EXAMPLE n This example illustrates various additive compositionsprepared in accordance with the present invention. These compositionswere prepared as described in Example I.

ADDITIVE A Ingredient: Amount, in part Water 87.5 Hydrotrope -2. 1.0sequestering agent 1 0.5 sequestering agent 2 10.0 Nonionic surfactant A0.5 Nonionic surfactant C 1 0.5

ADDITIVE B Ingredient: Amount, in parts Water 45.5 Hydrotrope 3.0sequestering agent 1 2.5 sequestering agent 2 40.0 Nonionic surfactant A4.5 Nonionic surfactant B 4.5

ADDITIVE C Ingredient: Amount, in parts Water 54.0 Hydrotrope 7.5sequestering agent 1 1.5 Sequestering agent 2 30.0 Nonionic surfactant A3.5 Nonionic surfactant B 3.5

1 A polyoxyethylene-polyoxypropylene block copolymer having an averagemolecular weight of about 2000 and containing about by weight ofethylene oxide.

EXAMPLE III This example illustrates the low foam properties of theadditives of the present invention.

From each of the compositions of Examples I and II, a typical aqueoususe solution was prepared. Specifically, four 2% by Weight caustic sodasolutions had added thereto, respectively, 0.125% by weight of theadditive of Example I, 0.5% by weight of additive A, 0.05% by weight ofadditive B, and 0.25% by Weight of additive C.

Each of the typical use solutions were tested for foam propagation by anaeration foam test. The test essentially comprises filling a one litergraduate cylinder with 300 mls. of test solution. A gas dispersion tubeequipped with a fritted glass disc of coarse porosity is then disposedin the graduate such that the base of the tube rests on the bottom ofthe graduate. Air is then introduced into the graduate through thedispersion tube at a rate of 400 cc. per minute, as determined by afiowmeter.

With air flowing through the graduate to obtain a reference level,protein soil, in this instance, homogenized whole egg is added to thesolution in 10 drop increments using a pipette-type medicine dropper.After five minutes of flowing air through the solution, the volume offoam above the solution is then measured and recorded.

The test is concluded after this procedure has been repeated to thepoint where either 90 drops of whole egg has been added or when the foamvolume exceeds 700 mls.

It has been found that when the foam level is less than 100 mls. in thepresence of 60 drops of whole egg (1% egg soil on a volume bases), thena satisfactory low foaming composition is provided.

6 The results of the tests run on the additives of the present inventionare set forth below in Table I.

It is seen from the data that over varying concentrations that theadditives of the present invention are ef fective foam inhibitors.

EXAMPLE IV This example illustrates the low foam synergistic propertiesof the present invention.

A series of comparative additives were prepared from the ingredients asset forth in Table II, below. From each of these additives was prepareda typical use solution containing 2% by weight of caustic soda and 0.125by Weight of additives.

A typical use solution was then prepared as above, but employing 0.125%by Weight of the additives of Example I. Each of the compositions werethen tested for foam propagation by the aeration foam'test described inExample III. The results of these tests are set forth in Table III,below.

It can be seen by comparing the'data of the product of Example I withthat from the compositions not employing all the ingredients,synergistic foam properties are obtained with the composition of thepresent invention.

TABLE IL-COMPARATIVE COMPOSITIONS Composition 1 2 3 4 Ingredient:

Water 44. 0 44. 0 49. 0 3B. 0 Hydrotrope- 9.0 9. 0 9. 0 9. 0sequestering agent:

1 2.0 2. 0 2. 0 2 40. 0 40. 0 40. 0 50. 0 NOIIIgJIQIC surfactant:

1 An ethylene oxide adduct 01 the propylene oxide condensate withethylenediamine having an average molecular weight oi about 7,500 andcontaining about 10% by Weight of ethylene oxide.

TABLE III.-FOAM PROPAGATION DATA Foam height, mls. oi-

- Example I Foam height, Mls.

Composition 1 2 3 4 No. drops egg soil:

EXAMPLE V weight of nonionic surfactant B, previously identified, beercopper pick-up tests were run. These tests were repeated using variousother compositions typically employed as cleaning compositions for brewkettles, as well as those of the present invention. These compositionswere as follows:

(E) A 2% caustic soda solution to which was added 0.25% of the additiveof Example I,

(F) A 2% caustic soda solution containing 0.5% of the product of ExampleI,

(G) A 3% caustic soda solution containing about 450 parts by weight ofsodium glucoheptonate, (H) A 3% caustic soda solution containing 5p.p.m. of

a,a,a"-amino tris-(methyl phosphonic acid).

The test procedure employed was as follows: Copper plates measuring 3.0"x 0.8 x 0.04, were initially cleansed and then immersed in 110 mls. ofthe test solution in sealed four ounce bottles, for both one hour andfive hours at both room temperature and 160 F.

After immersion the copper plates were expunged of any residual alkalinesolution by dipping them in 1:1 hydrochloric acid solution, rinsed withcopper-free distilled water and then immersed in a commercial beer,having an average copper content of 0.17 p.p.m. for two hours at roomtemperature.

After the two hour period, aliquot portions of the beer samples weretested for copper content thereby determining the amount of copper inthe plates that had been oxidized and/or dissolved. Copper content ofthe beer was determined by spectrophotometn'c analysis in accordancewith the Cuprethol Procedure as described by Brenner et al., AmericanSociety of Brewing Chemists Proceedings (1965), at pp. 187 to 193.

The results of these tests are set forth in the following table:

Copper pickup, p.p.m

Room temperature, 160 F., hours hours The data in the table clearlyevidences the superior copper corrosion inhibition properties of theproducts of the present invention since neither of the sequesteringagents alone approximate the properties of the combination thereof overthe varying temperature parameters.

What is claimed is:

1. A liquid additive composition consisting essentially of:

(a) a hydrotrope which is an alkylphenol polyglycol ether phosphate inpotassium salt form having a viscosity of 120 centipoises at 25 C., aspecific gravity of 1.26, a pH of 8-10 in 5% aqueous solution and afreezing point of 20 C.;

(b) a mixture of sequestering agents, said mixture consisting of (l)u,ot',ot"-arnino tris-(methyl phosphonic acid) or the potassium orsodium salts thereof, and (2) an alkali metal salt of a sugar acid, ormixtures thereof, the sequestering agents being present in a wherein yis an integer sufficiently large to insure that the ethylene oxideconstitutes a maximum of about 10% by weight of the total molecularweight of the molecule, the molecular weight of the molecule rangingfrom about 900 to 7800 and (2) an ethoxylated linear alcohol having fromabout 10 to 20 carbon atoms, the ethylene oxide being from about 20 toby weight of the total molecular weight of the molecule, apolyoxyethylene-polyoxypropylene block copolymer corresponding to theformula:

having a molecular weight of from about 900 to 4500 and wherein a;+c aresufficiently large such that the ethylene oxide being from about 0 to10% of the total molecular weight of the compound or mixtures thereof,the nonionic surfactant mixture being present in a weight ratio ofnonionic (1) to nonionic (2) of from about 1:2 to 2:1 and ((1) water.

2. The composition of claim 1 wherein said composition comprises, byweight:

(a) from about 1 to 9 percent of said hydrotrope,

(b) from about 7 to 48 percent of said mixture of sequestering agents,

(c) from about 1 to 10 percent of said mixture of now ionic surfactants,and

(d) from about 33 to 91 percent of water.

3. The composition of claim 1 wherein the alkali metal salt of the sugaracid is selected from the group consisting of sodium gluconate,,sodiumglucoheptonate and mixtures thereof.

4. A use solution for cleaning-in-place system consisting of:

(a) 130m about 5,000 to 50,000 p.p.m. of liquid caustic so a,

(b) from about 500 to 100,000 p.p.m. of the additive of claim 1, and

(c) the balance being water.

5. A liquid caustic soda solution containing from about 0.05 to 10% byweight of the additive of claim 1.

References Cited UNITED STATES PATENTS 3,278,446 10/ 1966 Irani 252--5452,992,187 7/1961 Gershon 252-156 3,235,627 2/1966 Mansfield 252-89 X2,674,619 4/1954 Lundsted 252- X 2,979,528 4/ 1961 Lundsted 2521 10 XMAYER WEINBLA'IT, Primary Examiner U.S. Cl. X.R;

